Fuse for low and high voltage current



March 30, 1954 F DRIESCHER 2,673,911

FUSE FOR LOW AND HIGH VOLTAGE CURRENT Filed Dec. 29, 1949 INVENiOR; FRITZ DIP/ESCHEQ,

BY 57% l v Patented Mar. 30, 1954 FUSE FORLOW AND HIGH VOLTAGE CURRENT Fritz Drieschef', Rheydt, Germany Application ,0ctoben29, 1949, SerialNo. 124,332

Claims priority; application Germany June 10, 1949 2 Claims.

The invention relates to fuses for use in circuits which are subject to'overloading.

Theinvention has among its objects to provide afuse structure that is safe'and effective in use over protracted periods oftime. Desirable features for fuse structures of this type include effective melting of selected fuse parts upon the occurrence of a predetermined overload and after thepassage of a prescribed time lag,- and these features aregenerally found so that it will, upon meltingof theblowpoint in fuses now in use. However, present fuses do not function satisfactorily if the circuits are subjected to substantial changes. in amperage values; some react too fast and others too slow in the predetermined overload range, still others are subject to sparking.

It is therefore the principal aim of the invention to avoid the deficiencies enumerated in the foregoing, and to provide an automatically operating efficient fuse.

The invention accordingly comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in a construction hereinafter set forth and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description, taken in connection with the accompanying drawings, in which the single figure is a vertical sectional view of a fuse constructed in accordance with the invention.

In carrying the invention into effect in the embodiment which has been selected for illustration in the accompanying drawing and for description in this specification and referring now particularly to the figure there is provided a casing having an endless wall 3, and opposite end walls I and 2. The wall 3 may preferably be made of material insulating against heat and/or electricity. The casing encloses a chamber that may be filled with a substance, for instance extinguishing material 5.

The end walls I and 2 may be made of conducting material and have projections to form connections, such as contact terminals or leads, for interconnection to an electric source (not shown). A conductor, such as a fuse wire 4, extends throughout the length of the chamber and is interconnected at one of its ends to the conducting wall 2 and forms on its other end an extension 1 that projects through the other conducting wall l and is insulated therefrom by means of an insulating plug 6. Said extension l -may be reinforced in relation to the fuse wired. At the free end, said-extension. 1 carthe like.

A spring 9V is connected at one side to the blow point 8 and is secured with its otherside to. the conductor wall. I and .is electrically interconnected thereto. Thespring 1Iis pre-tensioned 8', move from the active position shown in solid lines in .the figure to an inactive positionshown in broken lines in that. view. The. springs, the blow point 8, the extension 1, the fusewire 4., and the conductor wall 2 are arranged to be connected in series in an electric circuit.

The spring 9 is so composed that the safety device is actuated, namely the said circuit is interrupted within a temperature range of from 1'76--266 F.; this arrangement thus also provides for protection against outer heat sources.

In operation, the conductor walls I and 2 are interconnected to an electrical apparatus (not shown), and through that, to an electric source. While normal current flows through the fuse circuit, no change will take place. However, at the occurrence of an overload of predetermined value, the blow point 8 will be heated. Thereupon, the spring 9 will snap into the inactive position shown in broken lines in said figure, thus interrupting the circuit.

In the embodiment shown, the fuse wire 4 has a second extension arranged oppositely to the first extension 1 and pro ecting through the conductor wall 2. Insulating walls II are provided in the casing adjacent and connected to the walls I and 2, and said walls 1 and 2 furthermore are interconnected electrically by a second circuit that comprises a second fuse wire Ill. The fuse wire 4, on the other hand, is insulated, by means of plugs 6, from contact with the walls I I.

The fuse wire I0 is so dimensioned, in relation to the dimensions of the parts of the first circuit, that upon the occurrence of a predetermined overload the said first circuit will be interrupted before the second, by the melting of one or both blow points. Thereafter, since the entire overload is then applied to the second fuse wire Ill, it will melt at one point or another, thus finally interrupting the current.

In practice, fuses of this type have been found effective in interrupting current within a time lag of ten minutes upon the occurrence of a thirty per cent (30%) overload. However, it may be preferable to dimension the parts so that 9 \J' an overload of eighty per cent (80%) causes interruption within a time lag of ten minutes; at an overload of fifty per cent (50%) or more, the temperature range within which there will occur interruption of current is from l67-176 F. Fatigue of the circuit elements, and the consequences thereof, are eliminated by the low operating temperature of the device.

Since certain changes may be made in the above article and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A fuse device comprising a hollow-nonconductive casing, a pair of spaced conductive elements secured to said casing, a first fuse wire within said casing and having one end connected to one of said conductive elements, the other end of the first fuse wire having a blow point, means conductively connecting said blow point with the other of said conductive elements and resiliently biased in a direction away from said blow point so as to rupture the blow point when the latter softens due to heat, and a second fuse wire connected at its opposite ends to said conductive elements.

2. In a fuse structure, a casing formed by a non-conductive hollow member and two current conductive side walls, a first fuse wire disposed in said casing and having one end projecting outwardly from one side wall and insulated therefrom, a blow point secured to the end of said extension, a conductive spring secured at one end to said one side wall and connected at the opposite end to said blow point, said spring being sufflciently pretensioned to move to a position spaced from said extension upon melting of said blow point, the other side wall being connected to the other end of said first fuse wire, and a second fuse wire disposed in said casing and conductively connected at its opposite ends to said side walls and being so dimensioned with respect to said first fuse wire and blow point that an increase in current of a predetermined value through the fuse structure will melt said blow point and will thereafter melt said second fuse wire.

FRITZ DRIESCHER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 683,639 Crockett Oct. 1, 1901 867,496 Geisenhoner Oct. 1, 1907 1,469,767 Bogle Oct. 9, 1923 1,539,870 Sandin June 2, 1925 2,159,423 Bussmann May 23, 1939 2,293,953 Taylor Aug. 25, 1942 2,296,627 Brown Sept. 22, 1942 2,300,620 Duerkob Nov. 3, 1942 FOREIGN PATENTS Number Country Date 509,130 Great Britain July 11, 1939 

